Additively manufactured heat transfer device

ABSTRACT

An additively manufactured heat transfer device is disclosed, including an enclosure portion with outer walls. The outer walls contain an inner channel configured to direct a flow of coolant fluid. The heat transfer device further includes a fluid intake port and a fluid outtake port, each connected to the first inner channel. The fluid intake port is configured to direct a flow of coolant fluid through an outer wall of the enclosure portion into the inner channel, and the fluid outtake port is configured to direct a flow of coolant fluid through an outer wall of the enclosure portion out of the inner channel. The inner channel is defined by internal walls, and the enclosure portion and the internal walls form a single additively manufactured unit.

FIELD

This disclosure relates to systems and methods for transferring heat.More specifically, the disclosed embodiments relate to cold plates forelectronics systems.

INTRODUCTION

Thermal management is a growing field, partially driven by advancementsin electronics design that result in greater heat flux density fromsmaller and more powerful equipment. Effective thermal managementimproves both performance and reliability of electronics, and can becritical to system function. For instance, satellite circuit boards arehighly power dense and rely on redundant thermal systems to providenecessary heat dissipation even when regular maintenance is notpossible. Thermal management is also important in many other industriesinvolving other heat generating mechanical and/or chemical processes.

A variety of cooling technologies have been developed, but use of aliquid coolant is particularly effective due to a high heat transfercoefficient. Often, liquid cooling is accomplished with a cold plate, aconductive plate that acts as a heat transfer interface between a heatsource and channels of flowing liquid coolant. However, existing coldplate systems can be expensive and prone to leakage.

Efficient cold plates can have complex internal geometries and delicatestructures such as micro-channels, which result in costly andtime-consuming manufacture. In traditional manufacturing methods,forming channels for coolant flow typically requires joining throughwelding, brazing, or mechanical fastening. Such joins complicatemanufacture and may be more prone to failure. For function-criticalthermal management systems, a failure can have costly consequences.

SUMMARY

The present disclosure provides systems, apparatuses, and methodsrelating to additively manufactured heat transfer devices. In someembodiments, a heat transfer device may include an enclosure portionhaving outer walls. The outer walls may contain an inner channelconfigured to direct a flow of coolant fluid. The heat transfer devicemay further include a fluid intake port and a fluid outtake port, eachconnected to the first inner channel. The fluid intake port may beconfigured to direct a flow of coolant fluid through an outer wall ofthe enclosure portion into the inner channel, and the fluid outtake portmay be configured to direct a flow of coolant fluid through an outerwall of the enclosure portion out of the inner channel. The innerchannel may be defined by internal walls, and the enclosure portion andthe internal walls may form a single additively manufactured unit.

In some embodiments, a heat transfer device may include a housing havinga planar heat transfer face, and an internal wall structure forming achannel inside the housing. The channel may be configured to conductheat from the heat transfer face to a fluid. The housing and internalwall structure may form a single additively manufactured unit.

A method of manufacturing a heat transfer device may include printing ahousing having an external heat transfer face. The method may furtherinclude printing an internal wall structure that defines an innerchannel. The inner channel may be configured to channel fluid forcooling the heat transfer face.

Features, functions, and advantages may be achieved independently invarious embodiments of the present disclosure, or may be combined in yetother embodiments, further details of which can be seen with referenceto the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an illustrative additively manufacturedcold plate in accordance with aspects of the present disclosure.

FIG. 2 is another schematic diagram of the cold plate of FIG. 1.

FIG. 3 is an isometric view of another illustrative cold plate asdescribed herein.

FIG. 4 is a cutaway isometric view of the cold plate of FIG. 3, cutalong line 4-4.

FIG. 5 is a cutaway isometric view of the cold plate of FIG. 3, cutalong line 5-5.

FIG. 6 is a cutaway isometric view of the cold plate of FIG. 3, cutalong line 6-6.

FIG. 7 is a cross sectional view of the cold plate of FIG. 3, along line7-7

FIG. 8 is a cutaway isometric view of another illustrative cold plate asdescribed herein.

FIG. 9 is a cutaway isometric view of the cold plate of FIG. 8, cutalong line 9-9.

FIG. 10 is a partially exploded view of an illustrative cooling systemas described herein.

FIG. 11 is an isometric view of an illustrative cold plate quadrant.

FIG. 12 is a cutaway isometric view of the cold plate quadrant of FIG.11.

FIG. 13 is a flow chart depicting steps of an illustrative method ofadditive manufacture according to the present teachings.

FIG. 14 is a schematic diagram of an illustrative additive manufacturingapparatus as described herein.

FIG. 15 is a flow chart depicting steps of an illustrative method foradditively manufacturing a cold plate according to the presentteachings.

FIG. 16 is a flow chart depicting steps of an illustrative method forremoving heat from a transmitter according to the present teachings.

DETAILED DESCRIPTION

Various aspects and examples of heat transfer devices and relatedsystems and methods are described below and illustrated in theassociated drawings. Unless otherwise specified, a heat transfer devicein accordance with the present teachings, and/or its various componentsmay, but are not required to, contain at least one of the structures,components, functionalities, and/or variations described, illustrated,and/or incorporated herein. Furthermore, unless specifically excluded,the process steps, structures, components, functionalities, and/orvariations described, illustrated, and/or incorporated herein inconnection with the present teachings may be included in other similardevices and methods, including being interchangeable between disclosedembodiments. The following description of various examples is merelyillustrative in nature and is in no way intended to limit thedisclosure, its application, or uses. Additionally, the advantagesprovided by the examples and embodiments described below areillustrative in nature and not all examples and embodiments provide thesame advantages or the same degree of advantages.

This Detailed Description includes the following sections, which followimmediately below: (1) Overview; (2) Examples, Components, andAlternatives; (3) Illustrative Combinations and Additional Examples; (4)Advantages, Features, and Benefits; and (5) Conclusion. The Examples,Components, and Alternatives section is further divided into subsectionsA through F, each of which is labeled accordingly.

Overview

In general, a heat transfer device in accordance with the presentteachings may include a metal structure with a first surface configuredfor thermal communication with an electronics system and a secondsurface configured for thermal communication with a fluid. The heattransfer device may be configured to conduct heat from the electronicssystem to the fluid. The heat transfer device may be a single additivelymanufactured unit. The heat transfer device may also be referred to as aheat dissipation device, a heat exchanger, a heat sink, and/or a coldplate.

FIGS. 1 and 2 are schematic diagrams of an illustrative cold plate 10,which includes an enclosure portion or housing 12 having a first innerchannel 14 and a second inner channel 16. FIG. 1 is diagram of across-section of the cold plate, through the housing and the first innerchannel. Housing 12 includes outer walls 18 that contain the first andsecond inner channels, and includes side walls 20A, 20B and a conductivewall 22. In the present example, the outer walls further include asecond conductive wall 24. Conductive walls 22, 24 may also be referredto as heat transfer sides, thermal plates, and/or heat sinks. In someexamples, conductive wall 22 may be referred to as a cold plate and coldplate 10 may be referred to as a cold plate system or heat dissipationdevice.

First conductive wall 22 and second conductive wall 24 are opposing, andeach include an external heat transfer surface 26 and an internal heattransfer surface 28. The external transfer surface is configured todirectly or indirectly contact a heat source, thereby allowing therespective conductive wall to conduct heat away from the source. Theinternal transfer surface may be referred to as forming a portion ofeach inner channel 14, 16 and/or being in contact with each innerchannel. The internal transfer surface contacts a coolant fluid 30, andallows heat to be conducted from the conductive wall into the coolantfluid.

Each conductive wall 22, 24 has a thickness, which may be defined as anaverage distance between external transfer surface 26 and internaltransfer surface 28. The thickness of the conductive wall may bedetermined by desired thermal properties of cold plate 10 in combinationwith corresponding thermal properties of a material or materials of theconductive wall and of the coolant. The thickness of each conductivewall may also be defined as a distance between external heat transfersurface 26 and internal transfer surface 28 at any particular point, andmay vary over the conductive wall. The thickness of each conductive wallmay vary according to a pattern corresponding to the heat source,according to a pattern having a desirable thermal effect, and/or as aresult of a selected shape of the inner channels.

Each external heat transfer surface 26 may be substantially planar,shaped according to desired thermal properties, and/or shaped to conformto a surface of a heat source. Housing 12 may be generally rectangular,shaped according to desired thermal properties, and/or shaped tocorrespond to the heat source surface. In some examples, housing 12 maybe configured for thermal communication with the heat source through anintermediate component such as a heat spreader and/or thermal paste.

As shown in FIG. 1, a first fluid intake port 32 and a first fluidouttake port 34 are connected to channel 14. Coolant fluid 30 isdirected through a side wall 20A into channel 14 by intake port 32, andthen out of the channel through another side wall 20B by outtake port34. The coolant flows through channel 14 as indicated by arrow AA. Inthe depicted example, the coolant flows straight across cold plate 10 ina single stream. In some examples, coolant flow AA may double backand/or include branching streams. The coolant fluid may flow parallel toconductive walls 22, 24 and/or transfer surfaces 26. Any flow patternmay be used, as defined by a path or configuration of channel 14.

Inner channel 14 may have any cross-sectional shape and/or any pathcontained by outer walls 18. The channel may be configured to provide adesired flow pattern, accommodate a particular coolant type, and/or tofacilitate additive manufacture without interior secondary supports. Forexample, inner channel 14 may have a diamond cross-sectional shape. Foranother example, inner channel 14 may have curved corners and across-sectional dimension selected to facilitate laminar flow of ahigh-viscosity coolant fluid.

Intake port 32 and outtake port 34 may be any appropriate structure,including but not limited to valves, mechanical fittings, and/or digitalflow controls. The ports may be manufactured as part of housing 12, ormay be separately manufactured and installed into the housing. In someexamples, housing 12 may include a threaded aperture or other featureconfigured to mate with standard port parts.

As shown in FIG. 2, second inner channel 16 is connected to a secondfluid intake port 36 and a second fluid outtake port 38. FIG. 2 is aschematic plan view of cold plate 10, showing the first and second innerchannels as dashed to indicate their disposition behind conductive wall22. First inner channel 14 is separated from second inner channel 16 byan internal wall structure 40 of housing 12. In the present example,inner wall structure 40 is a single wall, spanning between side wall 20Aand side wall 20B to define rectangular inner channels 14, 16. Innerwall structure 40 may include multiple walls, to define any desiredshape and/or path of one or more inner channels.

First inner channel 14 is not in fluid communication with second fluidchannel 16, but there may be thermal communication between the channels.The two inner channels may each provide equivalent cooling functionalityto cold plate 10, may fulfill distinct cooling functions, and/or mayconstitute primary and back-up systems. Cold plate 10 may include anyappropriate number of separate inner channels. Each inner channel maycontact or comprise a portion of internal transfer surface 28 of eitherconductive wall 22 or conductive wall 24, or may contact or comprise aportion of the internal transfer surfaces of both conductive walls. Theinner channels may be referred to as contacting one or both conductivewalls.

Coolant fluid 30 is supplied to first inner channel 14 by a first fluidsystem including a pump 42 and a coolant fluid source 44. Coolant fluidsmay include, but are not limited to dielectric liquid coolants such assilicone oils, non-dielectric liquid coolants such as aqueous solutionsof ethylene glycol, and/or newer coolants such as nanofluids or ionicliquids. In the depicted example, coolant fluid source 44 recyclescoolant fluid output from outtake port 34. Source 44 may be configuredto transfer heat from the output coolant fluid to ambient air, to awaste heat recovery unit, and/or to any appropriate system. In someexamples, coolant fluid 30 and/or some portion of the coolant fluid mayundergo a phase change as a result of heat absorbed from cold plate 10.In such examples, source 44 may be configured to return coolant fluid 30to a liquid phase. Any appropriate coolant fluid source may be used.

Coolant fluid 30 is supplied to second inner channel 16 by a secondfluid system with a separate pump 42 and coolant fluid source 44. Insome examples, second inner channel 16 may be supplied with a differentcoolant fluid and/or a coolant fluid at a different temperature,pressure, etc. Second inner channel 16 and the second fluid system mayprovide fail-safe redundancy to cold plate 10. The cold plate may beconfigured for concurrent or alternate use of the first and second fluidsystems. In some examples, cold plate 10 may provide consistent coolingprior to and subsequent to failure of one of the fluid systems. In someexamples, cold plate 10 may provide reduced but sufficient coolingsubsequent to failure of one of the fluid systems.

Cold plate 10 may include further structures not depicted in FIGS. 1 and2. For example, the cold plate may include attachment featuresconfigured to attach the cold plate directly or indirectly to a heatsource. For instance, tabs with fastener apertures may be formed on sidewalls 20A, 20B to allow cold plate 10 to be fastened to an electronicssystem. For another instance, conductive wall 24 may be replaced by anintegrated I-beam structure configured to act as a structural beam of anelectronics case.

In another example, cold plate 10 may include structures with radiofrequency (RF) functionality or structures configured to interface witha transmitter, receiver, and/or transceiver. For instance, housing 12may be shaped to act as an antenna and include an adaptor for anamplifier connection. For another instance, cold plate 10 may includeapertures extending through the cold plate from external transfersurface 26 of conductive wall 24 to external transfer surface 26 ofconductive wall 22, the apertures being separated from the innerchannels by inner wall structure 40 and configured to guide radiofrequency transmissions.

Cold plate 10 includes a thermally conductive material, which may be alaser sintered metal or a fused deposition molded metal. In someexamples, the cold plate may include aluminum, copper, titanium, and/oran alloy thereof. The cold plate may include multiple materials, or maybe produced from a single material. Thermal conductivity, specific heat,density, and phase transition temperatures, along with other factors,may be considered in selecting a material or combination of materialsfor cold plate 10. Appropriate or desirable materials may depend on anintended application of the cold plate, and a selected additivemanufacturing method.

Referring again to FIG. 1, cold plate 10 has a manufacturing orientationdefined by an axis 46, which may be perpendicular to conductive wall 22,conductive wall 24, and/or either external transfer surface 26. In someexamples, manufacturing axis 46 may be a vertical axis. In someexamples, manufacturing axis 46 may be chosen according to a shape ofinner channels 14, 16 such that the inner channels are effectivelydiamond shaped with respect to the manufacturing orientation. Forinstance, manufacturing axis 46 may form an angle of approximately 45degrees relative to a side of a square inner channel.

Cold plate 10 may comprise a plurality of layers, each layer beinggenerally perpendicular to manufacturing axis 46. Each layer may be thinand planar, and fused to or otherwise cohesive with adjacent layers.Variation from one layer to an adjacent layer may be limited. That is,dimensions of cold plate 10 may change gradually along manufacturingaxis 46. The cold plate may include no abrupt overhangs, where an abruptoverhang may be described as any downward-facing surface forming anangle of greater than approximately 45 degrees or greater thanapproximately 50 degrees with manufacturing axis 46. All features ofcold plate 10 may therefore be printed without need for secondarysupports.

In some examples, limited external secondary supports may be used whencold plate 10 has a manufacturing orientation with a corner of housing12 contacting a base plate of the additive manufacturing equipment. Sucha manufacturing orientation may be selected to preclude any need forinternal secondary supports in inner channels 14, 16.

In some examples, cold plate 10 may be post-processed from an additivelymanufactured blank. Abrupt overhangs or other features inappropriate toadditive manufacture may formed by machining or otherwisepost-processing the blank. In such examples, the additively manufacturedblank may include no abrupt overhangs and may be printed without use ofsecondary supports. For example, housing 12 including outer walls 18,inner wall structure 40, and inner channels 14, 16 may be printedwithout intake and outtake ports. Separately manufactured ports may beinstalled in the manufactured blank.

Thickness of any structure of cold plate 10, or an additivelymanufactured blank of the cold plate, may be bounded. In other words,the thickness may have an upper and/or a lower limit. Each layer of thecold plate may have limited area for any structure. The limit may beabsolute or relative. For example, internal wall structure 40 of housing12 may be limited to a thickness of less than 100 thousandths of an inch(“mils”), where 1 mil=0.001″, or the wall structure may be limited to10% of a length of the housing. Such restriction may prevent cracking ortearing of printed material due to stresses introduced in themanufacturing process and/or in subsequent cooling or other temperaturefluctuation.

For another example, internal wall structure 40 may be restricted to athickness of more than 20 mils. Such restriction may help to produce adesired print resolution and features of sufficient strength to maintaingeometric integrity through the additive manufacturing process.

In some examples, cold plate 10 may be designed to have an equivalentfunctionality as an existing cold plate design and may be configured toconnect to a generally matching coolant fluid supply and/or recyclingsystem as the existing cold plate design.

Cold plate 10 may include additional structures, configured tofacilitate functions of equipment acting as a heat source and/or tofacilitate efficient additive manufacture of the cold plate. In someexamples, cold plate 10 may include fewer structures or simplerstructures than those described herein. For example, cold plate 10 mayinclude only a single inner channel and associated intake and outtakeports.

Cold plate 10 may be partially or entirely unitary. In other words,housing 12, side walls 20A, 20B, conductive walls 22, 24, internal wallstructure 40, inner channels 14, 16, and/or any other portions of thecold plate may comprise a single structure. The cold plate may beadditively manufactured in one process, without need for assembly ofseparate parts. In some examples, two or more unitary sections of coldplate 10 may be separately manufactured and assembled to form the coldplate. The cold plate may also be manufactured without secondarysupports that require removal after manufacture.

Cold plate 10 may have improved reliability, as a result of unitaryconstruction. Failure modes related to connection or interaction ofparts may be eliminated. For example, coolant fluid with low surfacetension may not leak at connection or joins between parts. Improperlyapplied or temperature sensitive sealants may not cause containmentfailure of corrosive or toxic coolant fluids. Generally, potential foroperational complications may be reduced for a cold plate with fewercomponents.

Cold plate 10 may have a geometry configured to be repeatable. In otherwords, the geometry of the cold plate may be such that when multiplecopies of the plate are manufactured, each copy measures within adesired tolerance of the original design. In some examples the desiredtolerance may be 1 mil, may be 10 mil, or may be any appropriate size.Manufactured copies may also be true to shape. For example, a waveguideaperture designed to be circular may be consistently printed as circularand not elliptical.

Examples, Components, and Alternatives

The following sections describe selected aspects of exemplary additivelymanufactured cold plates as well as related systems and/or methods. Theexamples in these sections are intended for illustration and should notbe interpreted as limiting the entire scope of the present disclosure.Each section may include one or more distinct embodiments or examples,and/or contextual or related information, function, and/or structure.

A. Illustrative Diamond Channel Cold Plate

As shown in FIGS. 3-7, this section describes an illustrative additivelymanufactured cold plate 100. Cold plate 100 is an example of cold plate10, described above. As shown in FIG. 3, the cold plate includes arectangular housing 110 with outer walls 108 including four side wallsand two conductive walls. The two conductive walls may be described as atop conductive wall 112 and a bottom conductive wall 114, relative to avertical manufacturing axis 116.

The four side walls of housing 110 may be described as a right wall 120,a left wall 122, an input wall 124, and an output wall 126. Each sidewall has a planar external surface that is perpendicular to conductivewalls 112, 114 and parallel to manufacturing axis 116. The side wallsmay also be described as vertical walls.

Each of the conductive walls 112, 114 has a planar external heattransfer surface 118. The external transfer surfaces are parallel toeach other, and manufacturing axis 116 is perpendicular to the externaltransfer surfaces. The external transfer surfaces may also be referredto as planar heat transfer faces and/or first and second opposing heattransfer sides. Each external transfer surface is configured to contactand conduct heat away from a heat source.

For example, cold plate 100 may be used to cool an optical devicemounted in a satellite, an Infrared (IR) sensor included in a securitysystem, or an automotive battery. External transfer surfaces 118, andcold plate 100 may be shaped and sized for efficient thermal managementof a given application. For electrical equipment, the cold plate may bescaled to a chip level application up to a unit level. In the presentexample, external transfer surfaces 118 measure approximately 1 inch by1 inch. In some examples, the external transfer surfaces may havemaximum dimensions allowed by an additive manufacturing method orprinting equipment.

Cold plate 100 may be configured for manufacture by Direct Metal LaserSintering (DMLS), metal fused deposition modeling, or any effectiveadditive manufacturing process. The cold plate comprises an aluminumalloy in the present embodiment, but may include any conductive materialor materials.

As shown in FIG. 4, outer walls 108 of housing 110 contain a first innerchannel 128. As shown in FIG. 5, the outer walls further contain asecond inner channel 130. The first inner channel may be referred as anupper channel, and the second inner channel may be referred to as alower channel. As shown in FIGS. 4-6, upper channel 128 is separatedfrom lower channel 130 by an internal wall structure including aplurality of internal walls 132. Each channel is configured to direct aseparate flow of coolant fluid through cold plate 100, parallel toexternal transfer surfaces 118. The channels may be used concurrently oralternately to conduct heat from external transfer surfaces 118 to thecoolant fluid in one or both channels. Each channel is configured toconduct heat from both external transfer surfaces.

Referring again to FIG. 3, cold plate 100 includes two intake ports. Anupper intake port 136 connects through input wall 124 to upper channel128 and a lower intake port 134 connects through the input wall to lowerchannel 130. Similarly, cold plate 100 includes two outtake ports. Anupper outtake port 138 connects through output wall 126 to upper channel128 and a lower outtake port 140 connects through the output wall tolower channel 130.

In the present example, cold plate 100 is unitary. That is, outer walls108, internal walls 132, intake ports 134 and 136, and outtake ports 138and 140 are additively manufactured as a single-piece blank. The intakeand outtake ports are then machined to form the depicted cylindricalouter surface. In some examples, outer walls 108 and internal walls 132may form a single piece and the intake and outtake ports may beseparately manufactured and fastened, welded, or otherwise fixed to theouter walls.

FIG. 4 shows cold plate 100 cut away along line 4-4 to show upperchannel 128. The upper channel includes a left side-passage 142connected to intake port 136. A plurality of cross-passages 144 branchoff at regular intervals from side-passage 142 and extend across coldplate 100 to a right side-passage 146. Each side-passage extendsparallel to right wall 120 and left wall 122, and parallel to the otherside passage. Cross passages 144 extend perpendicular to theside-passages.

Left side-passage 142 extends from intake port 136 across a majority ofcold plate 100, but stops short of output wall 126. Right side-passage146 extends across cold plate 100 from input wall 124 to connect toouttake port 138 at output wall 126. Left side-passage 142, rightside-passage 146, and cross passages 144 all extend parallel to externaltransfer surfaces 118.

Upper channel 128 is configured to direct a flow of coolant fluid fromintake port 136 along left side-passage 142, some portion of the coolantfluid turning down each cross passage 144. The upper channel is furtherconfigured to direct the coolant fluid from cross passages 144 intoright side-passage 146 and down the right side-passage to outtake port138. Upper channel 128 is configured to transfer heat from both externaltransfer surfaces 118 to the directed flow of coolant fluid.

FIG. 5 shows cold plate 100 cut away along line 5-5 to show lowerchannel 130. The lower channel is similar to upper channel 128, butmirrored. Lower channel 130 includes a right side-passage 148 connectedto intake port 134. A plurality of cross-passages 150 branch off atregular intervals from side-passage 148 and extend across cold plate 100to a left side-passage 152. Each side-passage extends parallel to rightwall 120 and left wall 122, and parallel to each other. Cross passages150 extend perpendicular to the side-passages.

Right side-passage 148 extends from intake port 134 across cold plate100 to output wall 126. Left side-passage 152 extends from across-passage 150 spaced from input wall 124 across a majority of coldplate 100 to connect to outtake port 140 at output wall 126. Leftside-passage 152, right side-passage 148, and cross passages 150 allextend parallel to external transfer surfaces 118.

Lower channel 130 is configured to direct a flow of coolant fluid fromintake port 134 along right side-passage 148, some portion of thecoolant fluid turning down each cross passage 150. The lower channel isfurther configured to direct the coolant fluid from cross passages 150into left side-passage 152 and down the left side-passage to outtakeport 140. Lower channel 130 is configured to transfer heat from bothexternal transfer surfaces 118 to the directed flow of coolant fluid.

In FIG. 6, cold plate 100 is cut away along line 6-6 to show thecross-sectional shapes of cross passages 144 and 150. Cross passages 144of upper channel 128 alternate with cross passages 150 of lower channel130. Each cross passage has a matching diamond cross-sectional shape,which may also be referred to as a rhombus or lozenge. Each side of eachdiamond shape forms an angle of less than 45 degrees with a verticalline parallel to manufacturing axis 116. Corners of each diamond shapeare rounded, in particular top corners 154 and bottom corners 156.

Top corners 154 of cross passages 144 and 150 are formed in topconductive wall 112 by internal heat transfer surfaces. Bottom corners156 of cross passages 144 and 150 are formed in bottom conductive wall114 by internal heat transfer surfaces. In other words, cold plate 100is configured to transfer heat from external heat transfer surface 118of top conductive wall 112 to coolant fluid in cross passages 144 ofupper channel 128 and to coolant fluid in cross passages 150 of lowerchannel 130 through top corners 154. Similarly, cold plate 100 is alsoconfigured to transfer heat from an external heat transfer surface 118of bottom conductive wall 114 to coolant fluid in cross passages 144 ofupper channel 128 and to coolant fluid in cross passages 150 of lowerchannel 130 through bottom corners 156.

Each channel 128, 130 may be described as contacting both top conductivewall 112 and bottom conductive wall 114. Each channel may also bedescribed as equidistant from external transfer surface 118 of topconductive wall 112 and external transfer surface 118 of bottomconductive wall 114. The channels may thereby provide effectiveredundant and/or fail-safe cooling systems. In the event of a failure ofone channel, the other is configured to effectively cool both sides ofcold plate 100.

FIG. 7 is a cross-sectional view of cold plate 100 along line 7-7,through a cross passage 144 and facing toward input wall 124. It shouldbe noted that the rest of the plurality of cross passages 144 match theone depicted. Further, the plurality of cross passages 150 arevertically mirrored relative to the depicted cross passage 144, butotherwise matching the depicted cross passage.

As shown, left side-passage 142 and right side-passage 146 each have adiamond cross-sectional shape with four perpendicular sides of equallength and rounded corners. Each side-passage has a height that isapproximately half of a greatest height of cross passage 144. Openingsin the internal wall structure of cold plate 100 connect cross passage144 to each side passage.

The cross-sectional shape of cross passage 144 varies across cold plate100, changing from the elongate diamond shape shown in FIG. 6 to matchthe square diamond shape of left side-passage 142 and right side-passage146. Bottom corner 156 rises as the cross passage nears theside-passages, extending up at an angle of approximately 45 degrees tomeet a bottom corner of each side-passage.

The diamond cross-sectional shapes of side-passages 142, 146 and crosspassages 144, 150 may allow cold plate 100 to be additively manufacturedwithout secondary supports in the inner channels. Each interior surfaceof upper channel 128 and lower channel 130 may form an angle of 45degrees or less with a vertical line parallel to the manufacturing axisof the cold plate.

B. Illustrative Top-Fed Diamond Channel Cold Plate

As shown in FIGS. 8-9, this section describes another illustrativeadditively manufactured cold plate 200. Cold plate 200 is an example ofcold plate 10, described above. Cold plate 200 is also substantiallysimilar to cold plate 100 described above. Accordingly, similarstructures are indicated with corresponding reference numbers.

Cold plate 200 includes a rectangular housing 210 with outer walls 208,including a top conductive wall 212 and a bottom conductive wall 214.Each of the conductive walls 212, 214 has a planar external heattransfer surface 218.

Outer walls 208 further include four side walls: a right wall 220, aleft wall 222, an input wall 224, and an output wall 226. The outerwalls of housing 210 contain a first inner channel 228 and a secondinner channel 230. First channel 228 is separated from second channel230 by an internal wall structure including a plurality of internalwalls 232.

Cold plate 200 also includes two intake ports. A right intake port 234connects through input wall 224 to first channel 228 and a left intakeport 236 connects through the input wall to second channel 230.Similarly, cold plate 200 includes two outtake ports. A left outtakeport 238 connects through top conductive wall 212 to first channel 228and a right outtake port 240 connects through the conductive wall tosecond channel 230.

Each intake and outtake port extends vertically and perpendicular toexternal transfer surfaces 218. Intake ports 234 and 236 are disposedagainst input wall 224, and curve proximate bottom conductive wall 214to connect in line with the inner channels. Outtake ports 238 and 240connect to an opening in an upper portion of the corresponding innerchannel. Such vertical orientation may facilitate additive manufacturingof the intake and outtake ports without secondary support. In thepresent example, cold plate 200 is unitary. That is, outer walls 208,internal walls 232, intake ports 234 and 236, and outtake ports 238 and240 are additively manufactured as a single-piece.

As shown in FIG. 9, first channel 228 includes a right side-passage 246connected to intake port 234. A plurality of cross-passages 244 branchoff at regular intervals from side-passage 246 and extend across coldplate 200 to a left side-passage 242. Left side-passage 242 extendsacross cold plate 200 to outtake port 238, proximate output wall 226, asshown in FIG. 8.

First channel 228 is configured to direct a flow coolant fluid fromintake port 234 along right side-passage 246, some portion of thecoolant fluid turning down each cross passage 244. The first channel isfurther configured to direct the coolant fluid from cross passages 244into left side-passage 242 and down the right side-passage to outtakeport 238. First channel 228 is configured to transfer heat from bothexternal transfer surfaces 218 to the directed flow of coolant fluid.

Second channel 230 is similar to first channel 228, but mirrored. Thesecond channel includes a left side-passage 252 connected to intake port236. A plurality of cross-passages 250 branch off at regular intervalsfrom side-passage 252 and extend across cold plate 200 to a rightside-passage 248. Right side-passage 248 extends across cold plate 200to outtake port 240, proximate output wall 226.

Second channel 230 is configured to direct a flow of coolant fluid fromintake port 236 along left side-passage 252, some portion of the coolantfluid turning down each cross passage 250. The second channel is furtherconfigured to direct the coolant fluid from cross passages 250 intoright side-passage 248 and down the left side-passage to outtake port240. Second channel 230 is configured to transfer heat from bothexternal transfer surfaces 218 to the directed flow of coolant fluid.

Each channel 228, 230 may be described as contacting both top conductivewall 212 and bottom conductive wall 214. Each channel may also bedescribed as equidistant from external transfer surface 218 of topconductive wall 212 and external transfer surface 218 of bottomconductive wall 214. The channels may thereby provide effectiveredundant and/or fail-safe cooling systems. In the event of a failure ofone channel, the other is configured to effectively cool both sides ofcold plate 200.

FIG. 9 is a cutaway view of cold plate 200 along line 9-9, cut through across passage 244 and facing toward input wall 224. It should be notedthat the rest of the plurality of cross passages 244 match the onedepicted. Cross passages 244 of first channel 228 alternate with crosspassages 250 of second channel 230. Each cross passage has a matchingdiamond cross-sectional shape, which may also be referred to as arhombus or lozenge. Further, the plurality of cross passages 250 arevertically mirrored relative to the depicted cross passage 244, butotherwise matching the depicted cross passage.

As shown in FIG. 9, left side-passage 242 and right side-passage 246each have a diamond cross-sectional shape with four perpendicular sidesof equal length. The diamond cross-sectional shapes of side-passages242, 246 and cross passages 244, 250 may allow cold plate 200 to beadditively manufactured without secondary supports in the innerchannels. Each interior surface of first channel 228 and second channel230 may form an angle of 45 degrees or less with a vertical lineparallel to the manufacturing axis of the cold plate.

Openings in the internal wall structure of cold plate 200 connect crosspassage 244 to each side passage. The cross-sectional shape of crosspassage 244 varies across cold plate 200, changing from an elongatediamond shape in a central region, to match the square diamond shape ofleft side-passage 242 and right side-passage 246 at left and right ends.An upper corner rises from right side-passage 246, extending up at anangle of approximately 45 degrees. Similarly, a bottom corner rises tomeet left side-passage 242, extending up at an angle of approximately 45degrees.

C. Illustrative Cooling System

As shown in FIGS. 10-12, this section describes an illustrative coolingsystem 300. FIG. 10 is a partially exploded view of system 300, with aheat source 310. The heat source may include, but is not limited to, anengine, a battery, a chemical reaction chamber, and/or another heattransfer device. In some examples, heat source 310 may includeelectronics such as a printed circuit board, a microwave frequencytransceiver, and/or a digital phased array. Cooling system 300 may beused in any environment where heat source 310 is located. For instance,the cooling system may be used in a vehicle, on a satellite, or in amanufacturing plant.

Cooling system 300 includes a front cold plate 312 and a back cold plate314. Heat source 310 is sandwiched between the front and back coldplates, which transfer heat away from two opposing sides of the heatsource. Front cold plate 312 may be described as disposed on a frontside of the heat source and back cold plate 314 as disposed on a backside of the heat source, relative to a primary orientation of the heatsource. In the depicted example, heat source 310 and cold plates 312,314 are shown as rectangular. The cold plates may be any shapeappropriate to heat source 310, and may be disposed on any two surfacesof the heat source. In some examples, additional cold plates may beincluded in cooling system 300. For instance, the cooling system mayinclude five cold plates configured to contact five of six sides of aheat source having a cubic shape.

Cooling system 300 may be secured to heat source 310 and/or to adjacentstructures. Each cold plate 312, 314 may be coupled to the heat sourceand/or the other cold plate. For example, the heat source may be bonded,fastened, or otherwise secured to each cold plate. In some examples,back cold plate 314 may in turn be coupled to a structural mount of anadjacent structure.

Back cold plate 314 is an example of additively manufactured cold plate10, including inner channels configured to direct a flow of coolantfluid. In the present example, the back cold plate also includesstructural components appropriate to support the heat source andfacilitate connection with adjacent structures. Back cold plate 314 isconfigured to conduct heat away from the back side of heat source 310.The back cold plate may channel fluid from a coolant fluid source, whichmay be separate from or shared with front cold plate 312.

Front cold plate 312 is another example of additively manufactured coldplate 10, including inner channels configured to direct a flow ofcoolant fluid. An intake port 321 and an outtake port 323 direct coolantfluid into and out of one side of the cold plate. The inner channels offront cold plate 312 may be laid out in any appropriate pattern, andcoolant fluid may be directed in linear, radial, and/or branching flow.In some examples, front cold plate 312 may include a single continuousinner channel, may include two or more vertically stacked channels,and/or may include multiple interwoven channels such as described incold plates 100 and 200 above.

Front plate 312 further includes a plurality of passages or pass-throughapertures 320, extending from a back side to a front side of the coldplate. The apertures are closed to coolant fluid, and separate from theinner channels. Apertures 320 may be configured to allow access to heatsource 310 through front cold plate 312. For example, an aperture may bedisposed over an infrared sensor, a status-indicator light emittingdiode, a system reset button, or a memory card slot. Cables, tubing,fluids, and/or any appropriate structures or components may also passthrough apertures 320. For example, heat source 310 may be an electricmotor and electrical power may be delivered to heat source 310 by acable passed through one aperture, while a driveshaft extends from themotor through another aperture.

For another example, front cold plate 312 may include an aperture 320for each antenna element of a transmitter, aligned with the antennaelement. For each such aperture, a corresponding waveguide may bemounted on front cold plate 312 such that the aperture and waveguidecooperatively guide transmissions from the corresponding antenna elementof the transmitter. Alternatively or in addition, a waveguide structuremay be formed on an inner surface of each aperture 320. In other words,apertures 320 may be configured to allow passage and/or guidetransmission of electromagnetic radiation through front cold plate 312.

Some or all of the plurality of apertures 320 in front plate 312 mayalign with other components, radiation sources, and/or receivers of heatsource 310. Front cold plate 312 may be designed for a specific heatsource, with a pattern of apertures 320 corresponding to selectedcomponents of the heat source.

In the depicted example, front cold plate 312 is shown covering a fullextent of an upper surface of heat source 310. In some examples, frontcold plate 312 may cover only a limited portion of a surface of the heatsource, and cooling system 300 may further include one or more covers.The covers may be configured to protect heat source 310 fromenvironmental effects such dust, weather, or incident radiation. Thecovers may not be configured to direct a flow of coolant fluid, andtherefore may be disposed over portions of heat source 310 that generatelimited heat. For example, a cover may be a single layer of aluminum,manufactured separately from front cold plate 312. In some examples,each cover may be additively manufactured as part of front cold plate312, or may comprise a different material or materials to the coldplate.

Cooling system 300 may be designed according to a specific heat source,transmitter, and/or other equipment. For example, cold plates 312, 314may be shaped to contact areas of heat source 310 generating significantheat, while the cooling system may include covers appropriate to protectareas of the heat source generating limited heat. Apertures 320 may belocated to allow access to selected components of heat source 310.

In some examples, front cold plate 312 may be made up of separatelymanufactured sections. Each section may include inner channelsconfigured to direct a flow of coolant fluid. In addition to thesections, front cold plate 312 may include bridging structures, toconnect the sections such that these inner channels operate in series.In other words, each bridging structure may direct coolant fluid fromone section to the next. An interface structure, including an intakeport and an outtake port, may be mounted at one or more connections. Insome examples, cold plate sections may be connected such that the innerchannels of each section remain separate. Each section may channel fluidfrom a separate coolant fluid source, from an adjacent section, and/orfrom a shared coolant fluid source.

Assembling front cold plate 312 from separate sections may facilitatereplacement in the event of a failure. Print quality may also beimproved by limiting the size of any one printed section, avoidingproblems such as warping and cracking. In some examples, front coldplate 312 may be manufactured in sections due to size constraints ofavailable printing equipment. In some examples, front cold plate 312 maybe manufactured as two pieces, as multiple pieces of differing design,or according to any division appropriate to selected manufacturingequipment and/or cold plate design.

FIGS. 11-12 show an example of a quadrant 318 which, when assembled withthree matching quadrants and appropriate connective structures, may formfront cold plate 312 of cooling system 300. In the present example,quadrant 318 measures approximately 15 inches by 15 inches and iscomprised of laser sintered aluminum alloy. The quadrant includes ahousing with outer walls 324, including a front wall 326 and a back wall328. A planar external heat transfer surface 330 of back wall 328 isconfigured to contact a front side of heat source 310. Apertures 320extend through cold plate quadrant 318 perpendicular to external heattransfer surface 330, through both front wall 326 and back wall 328.

Along an edge of cold plate quadrant 318, structural attachment features332 are disposed. In the present example, the features include tabsextending from a side wall of the quadrant. The tabs each include afastener aperture, appropriate for fastening cold plate quadrant 318 toan adjacent quadrant. In some examples, attachment features 332 may beused to connect the quadrant to other components of cooling system 300,and/or a support structure. Cold plate quadrant 318 may include anystructural attachment features, disposed at any point on the quadrant.For example, an outer wall 324 of the quadrant may be shaped to form anI-beam for connection to other structural beams of a satellite.Structural attachment features 332 may be additively manufactured aspart of quadrant 318, and/or may be add as part of post-processing.

Outer walls 324 contain a first layer 334 and a second layer 336,divided by an internal wall 338. As shown in FIG. 12, a cutaway view ofthe quadrant, each layer is divided into plurality of channels 340 byribs 342. Each layer is configured to direct multiple flows of coolantfluid parallel to external heat transfer surface 330 of back wall 328.In some examples, channels 340 may branch or interconnect, outer walls324 may include a third layer, and/or quadrant 318 may include anyappropriate number and configuration of layers and channels.

In the depicted example, channels 340 are generally rectangular incross-section. To facilitate additive manufacture without use ofinternal printing supports, quadrant 318 has a non-verticalmanufacturing axis 348, shown in FIG. 11. In other words, quadrant 318is manufactured in an orientation such that channels 340 have a diamondcross-sectional shape relative to manufacturing axis 348. The axisextends at about 50 degrees relative to vertical. Manufacturing axis 348may be selected according to a spacing of ribs 342, such that eachplanar surface of quadrant 318 extends at less than approximately 45degrees relative to the manufacturing axis. That is, manufacturing axis348 may be oriented such that outer walls 324, internal wall 338, andribs 342 do not form any abrupt overhangs.

In order to manufacture quadrant 318 in such an orientation, limitedsecondary supports may be required. For example, a support column may beprinted between a base plate of a printer and back wall 328. Such simpleexternal supports may be easily removed subsequent to printing withoutimpacting integrity or print quality of quadrant 318. In some examples,channels 340 may be defined by internal wall 338 and ribs 342 to have adiamond cross section relative to vertical. In such examples,manufacturing axis 348 may be approximately vertical and cold platequadrant 318 may be manufactured entirely without secondary supports.

As shown in FIG. 12, each channel 340 follows a curved, bent, orcornered path from an input 344 to an output 346. In the presentexample, the input and output are open ends of cold plate quadrant 318,configured for connection to a bridging component. When assembled toform the front cold plate, input 344 of one quadrant is connected to anoutput 346 of another quadrant such that together the four quadrantsoperate in series with a single effective input and output. Eachbridging component may include a perpendicular channel connected to theinput or output such that channels 340 function similarly to the crosspassages described in cold plate 100. Any effective structures or fluidconnections may be used to assemble quadrant 318 into front cold plate312. The front cold plate may be configured for any effective coolantfluid flow pattern.

In the present example, first layer 334 of cold plate quadrant 318 isspaced from back wall 328. That is, second layer 336 is closer toexternal heat transfer surface 330 than first layer 334. Accordingly,first layer 334 may be configured to serve as a backup or fail-safesystem for second layer 336. During normal operation, coolant fluidflowing through second layer 336 may absorb heat directly through backwall 328 from the heat source. In the event of a failure, heat may beconducted from back wall 328 through ribs 342 of second layer 336 tointernal wall 338. Coolant fluid flowing through first layer 334 maythen absorb heat through internal wall 338.

Cold plate quadrant 318 further includes a plurality of bosses 350, eachhaving a central aperture 320. Each boss extends between front wall 326and back wall 328, perpendicular to the front and back walls. The bossesextend through first layer 334, internal wall 338, and second layer 336.The bosses may also be referred to as cylindrical passages, internalwall structures, and/or integrated waveguides. Apertures 320 may bedescribed as passages separated from the first and second layers by aninternal wall structure.

In the present example, all bosses 350 and apertures 320 are circularand of matching size. In some examples, bosses 350 may have a differentshape from apertures 320 or shape and/or size may vary among bosses 350and/or apertures 320. In some examples, bosses 350 may extend at anon-perpendicular angle relative to the front and back walls, to alignwith a component or function of the heat source, such as a transmissionor reception direction of a transceiver. For a transceiver, dimensionsof the apertures may be selected according to one or more transmissionfrequencies. For example, apertures 320 may be approximately acentimeter in diameter, appropriate to act as a waveguide for microwavefrequencies.

Each of the plurality of bosses 350 is disposed on a rib 342 between twochannels. In some examples, a boss may be disposed within a channel 340.Where a boss 350 is disposed on a rib 342, the boss forms part of therib separating the two adjacent channels 340. Each aperture 320 isseparated from coolant fluid in the surrounding or adjacent channels bythe corresponding boss 350. Positions of apertures 320 may be selectedaccording to the layout of the heat source. Ribs 342 may be accordinglypositioned and curved relative to bosses 350 such that no gaps areformed that are too small to be adequately resolved during additivemanufacture.

D. Illustrative Method of Additive Manufacture

This section describes steps of an illustrative method for additivemanufacture of a workpiece; see FIG. 13. Aspects of an illustrativeadditive manufacturing device depicted in FIG. 14 may be utilized in themethod steps described below. Where appropriate, reference may be madeto components and systems that may be used in carrying out each step.These references are for illustration, and are not intended to limit thepossible ways of carrying out any particular step of the method.

Additive Manufacturing (AM) is quickly gaining popularity in manyindustries as a method of rapid production at relatively low cost. AM,sometimes known as 3D printing, can be used to create a solid objectfrom a 3D model by building the object incrementally. AM typicallyapplies a raw material that is then selectively joined or fused tocreate the desired object. The raw material is typically applied inlayers, where the thickness of the individual layers can depend upon theparticular techniques used.

Often the raw material is in the form of granules or powder, applied asa layer and then selectively fused by a heat source. In many cases, theupper surface of a bed of such material is fused, and the growingworkpiece is then lowered slightly into the bed itself. A fresh layer ofraw material is then applied to the bed, and the next layer is fusedonto the previous one. The granular raw material may include for examplethermoplastic polymer, metal powder, metal alloy powder, or ceramicpowder, which may be fused using a computer-controlled heat source, suchas a scanning laser or scanning electron beam. Exemplary methods includeselective laser melting (SLM) direct metal laser sintering (DMLS),selective laser sintering (SLS), fused deposition modelling (FDM), andelectron beam melting (EBM) among others.

FIG. 13 is a flowchart illustrating steps performed in an illustrativeadditive manufacturing method, and may not recite the complete processor all steps of the method. Although various steps of method 400 aredescribed below and depicted in FIG. 13, the steps need not necessarilyall be performed, and in some cases may be performed simultaneously orin a different order than the order shown.

At step 410, digital information describing an ordered plurality oflayers is received. The digital information may be received by acomputer controller 512 of an additive manufacturing device 510 asdepicted in FIG. 14. The additive manufacturing device may also bereferred to as a printer, or a fabricator. Computer controller 512 mayinclude any data processing system configured to receive digital designinformation and control functions of printer 510. The illustrativecomputer controller shown in FIG. 14 includes a processor 514 forcontrolling printer functions and memory 516 for storing received data.

The received information may include geometric data and/or designdetails for a plurality of two-dimensional patterns that constitutelayers of a three-dimensional object, where the three-dimensional objectis a workpiece 528 to be manufactured. For example, workpiece 528 may bea cold plate as described above. The layers may also be described ascross-sections or slices. The plurality of layers is ordered, such thatthe layers may be numbered or organized from a first layer to a lastlayer.

Step 412 of method 400 includes depositing raw material on a buildplatform 518 located in a building environment 520 of printer 510. Thebuild platform may include a support moveable by computer controller 512along a manufacturing axis 522. The build platform may have a planarsurface perpendicular to manufacturing axis 522.

The raw material may be any material appropriate to additivemanufacturing, typically a fluid or powder and including but not limitedto photopolymer resin, thermoplastic, plaster, ceramic, and metal. For acold plate as described above, the raw material may be an alloy powderof a conductive metal such as aluminum or copper. The material may bedistributed from a raw material source 524 such as a hopper, a tank, ora powder bed. For example, aluminum powder may be swept from a powderbed over build platform 518 by a brush arm actuated by computercontroller 512.

The raw material may be distributed evenly over build platform 518, ormay be deposited in a selected pattern. Depositing may be done undercontrol of computer controller 512. In some examples, build platform 518may be submerged in raw material and depositing may be accomplished bygravity or fluid pressure. In some examples, a print head 526 connectedto raw material source 524 may deposit the raw material in a patterncorresponding to the first layer of the ordered plurality of layers.

At step 414, the raw material is altered to produce the first layer. Inother words, a physical change is induced the deposited material,according to the design information describing the first layer of theordered plurality of layers and as directed by the computer controller512, to realize the first layer as a physical object on the buildplatform.

The material may be acted on by a print head 526 of printer 510,controlled by computer controller 512. For example, the print head mayinclude a laser that cures a photopolymer by exposure to light. For thecold plates described above, print head 526 may be a laser that sintersa metal powder by exposure to heat, or a heated printer extruder headthat delivers a continuous filament of thermoplastic metal. The printhead may be directed by computer controller 512 to follow a pathdelineated in the received digital information for the first layer,and/or a path calculated by processor 514 based on the received digitalinformation.

Step 416 includes repositioning the build platform. In some examples,build platform 518 may start a selected distance from print head 526.The selected distance may be determined by the procedures performed bythe print head. Subsequent to production of a layer, the build platformmay be repositioned by computer controller 512 along manufacturing axis522 away from print head 526 by the layer's thickness. That is, thebuild platform may be moved such that a top surface of the producedlayer is the selected distance from print head 526.

In some examples, build platform 518 may start in alignment with anotherelement of printer 510 such as a raw material distribution component.Subsequent to production of a layer, the build platform may berepositioned by computer controller 512 along manufacturing axis 522such that a top surface of the produced layer is aligned with the otherelement of printer 510. In some examples, at step 416 print head 526 maybe repositioned instead of or in addition to build platform 518. In someexamples, step 416 may be skipped.

At step 418, raw material is deposited on the layer produced in thepreceding step of method 400. As described for step 412, the rawmaterial may be any appropriate material and may be deposited anyappropriate manner. At step 420, the raw material is altered to producethe next layer as previously described for step 414.

Steps 416 through 420 may be repeated to produce each layer of theplurality of layers of the received digital information, until the lastlayer is produced. The produced first through last layers may thencomprise workpiece 528 as described in the received digital information.The workpiece may be removed from the printer and post-processed asdesired. For example, a cold plate as described above may be machinedfrom a build plate of the build platform, fine details or smoothsurfaces of the exterior of the cold plate may be further finished bymachining or other methods, and then intake and outtake ports may beinstalled.

E. Illustrative Method of Manufacturing a Cold Plate

This section describes steps of an illustrative method 600 formanufacturing a cold plate; see FIG. 15. Aspects of cold plates, coldplate design, additive manufacturing methods, or additive manufacturingdevices described above may be utilized in the method steps describedbelow. Where appropriate, reference may be made to components andsystems that may be used in carrying out each step. These references arefor illustration, and are not intended to limit the possible ways ofcarrying out any particular step of the method.

FIG. 15 is a flowchart illustrating steps performed in an illustrativemethod, and may not recite the complete process or all steps of themethod. Although various steps of method 600 are described below anddepicted in FIG. 15, the steps need not necessarily all be performed,and in some cases may be performed simultaneously or in a differentorder than the order shown.

Conventional part designs used for machining or other traditionalmethods of manufacturing a cold plate may be inefficient or evenunworkable for additive manufacture. Depending on the process andmaterial used, unsupported features may collapse, delicate features maybe rendered with insufficient clarity, and/or wearing and cracking mayoccur. Internal channels and complex geometries generally rely onsecondary printing supports that require expensive and time-consumingremoval by hand. New cold plate designs and methods of manufacturingcold plates are needed to maintain the functionality of conventionalcold plates while enabling efficient use of AM methods.

Method 600 is an example of such a new method. At step 602, the methodincludes printing a housing with opposing external faces. The housingmay comprise a thermally conductive material, and may be sized tocorrespond to a heat source. The opposing external faces may beconfigured to conduct heat from the heat source, being planar or of anyappropriate shape.

Printing, of step 602 and of subsequent steps, may be done according toan additive manufacturing method such as method 400 described above. Inparticular, printing may be done by Direct Metal Laser Sintering (DMLS)or metal fused deposition modeling of an aluminum or copper alloy. Thehousing may have an axis perpendicular to the opposing external faces,which may coincide with a vertical direction or manufacturing axis ofthe additive manufacturing method. In other words, the housing may beprinted with the external faces flat. Printing may be carried outwithout use of secondary supports.

Step 604 includes printing an internal wall structure. The internal wallstructure may be disposed between the opposing external faces, andcontained by the housing.

The internal wall structure may include a plurality of surfaces, eachdownward-facing surface being disposed at an angle of less thanapproximately 45 degrees relative to the manufacturing axis.

At step 606, method 600 includes defining first and second innerchannels. The inner channels may be contained in the housing andseparated by the internal wall structure. The first and second innerchannels may be shaped to avoid a need for internal secondary supports.For example, the channels may have diamond cross-sectional shapes.

The inner channels may have complex paths, also defined by the internalwall structure. Each inner channel may extend from an input to anoutput, some portion of the channel extending parallel to one or both ofthe opposing external faces. Each inner channel may be configured todirect a separate flow of fluid through the housing, such that heatconducted by the opposing external faces is transferred into the fluid.

Step 608 includes printing first and second fluid intake and outtakeports. The first intake and outtake ports may be in fluid communicationwith the first inner channel, and the second intake and outtake portsmay be in fluid communication with the second inner channel. The intakeports may be configured for connection to a shared fluid supply and/orto separate fluid supplies. Each intake port may be configured to directflow of the fluid through an outer wall of the housing into thecorresponding inner channel.

Similarly, the outtake ports may be configured for connected to a sharedfluid exhaust system and/or separate fluid exhaust systems. Each outtakeport may be configured to direct flow of the fluid through an outer wallof the housing out of the corresponding inner channel.

In some examples, step 608 may instead include printing connections forintake and outtake ports and/or apertures through outer walls of thehousing appropriate to receive ports. The intake and outtake ports maybe additively manufactured, post-processed, and/or separately installed.

An optional step 610 includes defining a waveguide passage between theopposing external faces. The passage may be defined by the internal wallstructure printed in step 604, or step 610 may include printingadditional structures. Any number of additional waveguide passages maybe similarly defined.

The waveguide passage may be circular, rectangular, or any appropriateshape and may extend perpendicular to the opposing external faces. Aninternal dimension of the passage may be selected according to atransmission or reception frequency of the heat source. The passage maybe separated from the first and second inner channels and the flow offluid.

In some examples, method 600 may further include steps to post-processthe cold plate, such as machining, drilling, and/or surface finishing.Post-processing may include assembly of separately printed sections ofthe cold plate, such as the quadrants described above for illustrativetransmitter cooling system 300. Cold plate sections may be assembledsuch that channels of each section connect to form the first and secondchannels of the cold plate. Assembly may include bonding, fastening,and/or otherwise securing cold plate sections.

F. Illustrative Method of Removing Heat from a Microwave Transmitter

This section describes steps of an illustrative method 700 for removingheat from a microwave transmitter; see FIG. 16. Aspects of cold platesdescribed above may be utilized in the method steps described below.Where appropriate, reference may be made to components and systems thatmay be used in carrying out each step. These references are forillustration, and are not intended to limit the possible ways ofcarrying out any particular step of the method.

FIG. 16 is a flowchart illustrating steps performed in an illustrativemethod, and may not recite the complete process or all steps of themethod. Although various steps of method 700 are described below anddepicted in FIG. 16, the steps need not necessarily all be performed,and in some cases may be performed simultaneously or in a differentorder than the order shown.

At step 702, the method includes providing a cold plate with passagesorthogonal to a heat transfer surface. Such a cold plate may bemanufactured according to method 600, described above. The front coldplate of transmitter cooling system 300 described above is an example ofsuch a cold plate. The cold plate may include a housing and at least oneinternal channel, the internal channel being configured to direct a flowof fluid through the cold plate. The cold plate may be configured toconduct heat from the heat transfer surface through the housing to thefluid in the internal channel.

The provided cold plate may also be configured for a selectedtransmitter. For example, the passages may be disposed to correspond topositions of radiating elements of the transmitter. For another example,the heat transfer surface may be of a size and shape matching a heatgenerating portion of the transmitter.

Step 704 includes contacting the heat transfer surface of the cold platewith a transmitter. The cold plate may directly or indirectly contactthe transmitter, but may be in thermal communication with thetransmitter. For example, thermal paste may be disposed between the heattransfer surface and the transmitter to improve conduction. Once incontact, the heat transfer surface may conduct heat away from thetransmitter to fluid flowing through the cold plate.

Step 706 includes aligning the passages of the cold plate with elementsof the transmitter. The passages may be aligned with radiating elementsof the transmitter such as exciters or antennas. The cold plate maythereby allow transmission from the transmitter that might otherwise beblocked by conductive material or fluid of the cold plate. In someexamples, the passages may be configured to act as waveguides fortransmitted signals.

An optional step 708 includes sandwiching the transmitter between thecold plate and another cold plate. In some examples, the additional coldplate may include a heat transfer surface without orthogonal passages.The additional cold plate may accordingly be disposed in contact with aportion of the transmitter that does not include radiating elements. Insome examples, both cold plates may include orthogonal passages and maybe disposed in contact with radiating portions of the transmitter.

Illustrative Combinations and Additional Examples

This section describes additional aspects and features of an additivelymanufactured cold plate, presented without limitation as a series ofparagraphs, some or all of which may be alphanumerically designated forclarity and efficiency. Each of these paragraphs can be combined withone or more other paragraphs, and/or with disclosure from elsewhere inthis application, in any suitable manner. Some of the paragraphs belowexpressly refer to and further limit other paragraphs, providing withoutlimitation examples of some of the suitable combinations.

A0. An additively manufactured cold plate, comprising:

an enclosure portion including outer walls, the outer walls containing afirst inner channel configured to direct flow of a coolant fluid,

a first fluid intake port connected to the first inner channel, thefirst fluid intake port configured to direct flow of a coolant fluidthrough an outer wall of the enclosure portion into the first innerchannel, and

a first fluid outtake port connected to the first inner channel, thefirst fluid outtake port configured to direct flow of a coolant fluidthrough an outer wall of the enclosure portion out of the first innerchannel, wherein the first inner channel is defined by internal walls,the enclosure portion and the internal walls forming a single additivelymanufactured unit.

A1. The cold plate of A0, wherein the enclosure portion contains asecond inner channel configured to direct flow of coolant fluid, thesecond inner channel being connected to a second fluid intake port and asecond fluid outtake port, the first and second inner channels beingisolated from each other.

A2. The cold plate of A1, wherein each of the first and second intakeports is connected to a separate coolant fluid source.

A3. The cold plate of any of A1-A2, wherein each of the first and secondintake ports is connected to a separate pump device configured todeliver coolant fluid into the cold plate.

A4. The cold plate of any of A1-A3, wherein the enclosure portion hasfirst and second opposing heat transfer sides, each of the first andsecond inner channels being equidistant from the first and second heattransfer sides.

A5. The cold plate of any of A1-A3, wherein the enclosure portion hasfirst and second opposing heat transfer sides, the first inner channelbeing closer to the first heat transfer side than the second heattransfer side, the second inner channel being closer to the second heattransfer side than the first heat transfer side.

A6. The cold plate of any of A0-A5, wherein the enclosure portion hasfirst and second opposing heat transfer sides, the first inner channelbeing equidistant from the first and second heat transfer sides.

A7. The cold plate of any of A0-A6, wherein the first inner channel hasa diamond shaped cross-section configured to be manufactured by additivemanufacturing without any need for secondary supports.

A8. The cold plate of any of A0-A7, wherein the enclosure portion hasfirst and second opposing planar sides parallel to a direction of fluidflow through the first inner channel, and a first passage from the firstplanar side to the second planar side configured to guide microwavetransmission through the cold plate, wherein the passage has an internalwall structure separating the passage from the inner channel.

A9. The heat transfer device of A0, further including a structuralattachment feature, wherein the enclosure portion, the internal walls,and the structural attachment feature form a single additivelymanufactured unit.

B0. A heat dissipation device, comprising:

a housing having a planar heat transfer face, an internal wall structuredefining a first channel inside the housing configured to remove heatfrom the heat transfer face, the housing and internal wall structureforming a single additively manufactured unit.

B1. The heat dissipation device of B0, wherein the internal wallstructure defines a second channel inside the housing configured toremove heat from the heat transfer face.

B2. The heat dissipation device of B1, wherein the first and secondchannels are configured to alternate removing heat from the heattransfer face.

B3. The heat dissipation device of B1, wherein the first and secondchannels are configured to additively remove heat from the heat transferface.

C0. A method of manufacturing a heat dissipation device, comprising:

printing a first housing having an external heat transfer face, and aninternal wall structure defining a first inner channel configured forcooling the heat transfer face.

C1. The method of C0, wherein the first housing and internal wallstructure are formed of a single additively manufactured unit.

C2. The method of any of C0-C1, further comprising: printing a firstfluid intake port connected to the first inner channel, configured todirect flow of a coolant fluid through an outer wall of the firsthousing into the first inner channel, and

printing a first fluid outtake port connected to the first innerchannel, configured to direct flow of a coolant fluid through an outerwall of the first housing out of the first inner channel.

C3. The method of any of C0-C2, wherein the printing step includes:

defining a second inner channel configured for cooling the heat transferface, the first and second inner channels being isolated from eachother.

C4. The method of any of C0-C3, wherein the housing has a secondexternal face parallel and opposite from the external heat transferface, the printing step including:

defining a passage from the external heat transfer face to the secondexternal face, the passage being configured to guide microwavetransmission through the heat dissipation device.

C5. The method of any of C0-C4, further comprising:

printing a second housing having an external heat transfer face, and aninternal wall structure defining a first inner channel configured forcooling the heat transfer face, wherein the second housing is configuredfor assembly with the first housing on opposite sides of an electroniccircuit device.

D0. A method of removing heat from a microwave transmission device,comprising:

providing a first cold plate having a heat transfer surface and an innerwall structure defining a first channel configured to cool the heattransfer surface, and a plurality of passages running through the firstcold plate orthogonal to the heat transfer surface,

contacting the heat transfer surface of the first cold plate to amicrowave transmission device, and aligning the passages of the firstcold plate with microwave emitters on the microwave transmission device.

D0. The method of D0, further comprising:

sandwiching the microwave transmission device between the first coldplate and a second cold plate, each of the first and second cold platesbeing manufactured by additive manufacturing.

D2. The method of any of D0-D1, wherein the providing step includes:

printing the first cold plate including the heat transfer surface andthe inner wall structure.

E0. A cold plate, comprising:

a housing having a planar heat transfer face,

an internal wall structure forming a first channel inside the housingconfigured to conduct heat from the heat transfer face to a fluid, thehousing and internal wall structure forming a single additivelymanufactured unit.

E1. The cold plate of E0, wherein the internal wall structure defines asecond channel inside the housing configured to conduct heat from theheat transfer face to a fluid.

E2. The cold plate of E1, wherein the first and second channels areconfigured to alternate removing heat from the heat transfer face.

E3. The cold plate of any of E1-E2, wherein the first and secondchannels are configured to additively remove heat from the heat transferface.

E4. The cold plate of any of E1-E3, wherein the internal wall structureforms at least one passage through the cold plate, perpendicular to theheat transfer face, isolated from the first channel and configured forguiding radio transmission through the cold plate.

F0. A method of manufacturing a cold plate, comprising:

printing a first housing having an external heat transfer face, and aninternal wall structure defining a first inner channel configured tochannel fluid for cooling the heat transfer face.

F1. The method of F0, wherein the first housing and internal wallstructure are formed of a single additively manufactured unit.

F2. The method of any of F0-F1, further comprising:

printing a first fluid intake port connected to the first inner channel,configured to direct flow of a coolant fluid through an outer wall ofthe first housing into the first inner channel, and

printing a first fluid outtake port connected to the first innerchannel, configured to direct flow of a coolant fluid through an outerwall of the first housing out of the first inner channel.

F3. The method of any of F0-F2, wherein the printing step includes:

forming a second inner channel configured for cooling the heat transferface, the first and second inner channels being isolated from eachother.

F4. The method of any of F0-F3, wherein the first housing has a secondexternal face parallel and opposite the external heat transfer face, theprinting step including:

defining a passage from the external heat transfer face to the secondexternal face, the passage being configured to guide radio transmissionthrough the cold plate.

F5. The method of any of F0-F4, further comprising:

printing a second housing having an external heat transfer face, and aninternal wall structure defining a first inner channel configured forcooling the heat transfer face, wherein the second housing is configuredfor assembly with the first housing on opposite sides of an electroniccircuit device.

Advantages, Features, and Benefits

The different embodiments and examples of the additively manufacturedcold plates described herein provide several advantages over knownsolutions for thermal management of electronics. For example,illustrative embodiments and examples described herein allow manufactureof a cold plate with reduced manual assembly.

Additionally, and among other benefits, illustrative embodiments andexamples described herein allow manufacture of a cold plate with highlycomplex internal channels, including fail safe redundant loops.

Additionally, and among other benefits, illustrative embodiments andexamples described herein allow a cold plate with channels formed in aunitary structure, without joins or fastenings.

Additionally, and among other benefits, illustrative embodiments andexamples described herein may have improved operational reliability.

No known system or device can perform these functions, particularlywithout internal secondary printing supports. However, not allembodiments and examples described herein provide the same advantages orthe same degree of advantage.

Conclusion

The disclosure set forth above may encompass multiple distinct exampleswith independent utility. Although each of these has been disclosed inits preferred form(s), the specific embodiments thereof as disclosed andillustrated herein are not to be considered in a limiting sense, becausenumerous variations are possible. To the extent that section headingsare used within this disclosure, such headings are for organizationalpurposes only. The subject matter of the disclosure includes all noveland nonobvious combinations and subcombinations of the various elements,features, functions, and/or properties disclosed herein. The followingclaims particularly point out certain combinations and subcombinationsregarded as novel and nonobvious. Other combinations and subcombinationsof features, functions, elements, and/or properties may be claimed inapplications claiming priority from this or a related application. Suchclaims, whether broader, narrower, equal, or different in scope to theoriginal claims, also are regarded as included within the subject matterof the present disclosure.

What is claimed is:
 1. An additively manufactured heat transfer device,comprising: an enclosure portion including outer walls, the outer wallscontaining a first inner channel configured to direct flow of a coolantfluid, a first fluid intake port connected to the first inner channel,the first fluid intake port configured to direct flow of a coolant fluidthrough an outer wall of the enclosure portion into the first innerchannel, a first fluid outtake port connected to the first innerchannel, the first fluid outtake port configured to direct flow of thecoolant fluid through an outer wall of the enclosure portion out of thefirst inner channel, wherein the first inner channel is defined byinternal walls, the enclosure portion and the internal walls forming asingle, monolithic additively manufactured unit, and at least onepassage configured to guide electromagnetic signals through the heattransfer device.
 2. The heat transfer device of claim 1, wherein theenclosure portion contains a second inner channel configured to directflow of a coolant fluid, the second inner channel being connected to asecond fluid intake port and a second fluid outtake port, the first andsecond inner channels being isolated from each other.
 3. The heattransfer device of claim 2, wherein the enclosure portion has first andsecond opposing heat transfer surfaces, the first inner channel beingcloser to the first heat transfer surface than the second heat transfersurface, the second inner channel being closer to the second heattransfer surface than the first heat transfer surface.
 4. The additivelymanufactured heat transfer device of claim 2, wherein the first andsecond inner channels are configured to additively remove heat from anexternal heat transfer surface.
 5. The heat transfer device of claim 1,further including a structural attachment feature, wherein the enclosureportion, the internal walls, and the structural attachment feature forma single additively manufactured unit.
 6. The heat transfer device ofclaim 1, wherein the enclosure portion has first and second opposingplanar sides parallel to a direction of fluid flow through the firstinner channel, wherein the at least one passage is from the first planarside to the second planar side and is configured to guide microwavetransmission through the heat transfer device, and wherein the at leastone passage has an internal wall structure separating the at least onepassage from the first inner channel.
 7. The additively manufacturedheat transfer device of claim 1, wherein the at least one passagethrough the heat transfer device extends from a first heat transfer faceto a second external face, perpendicular to the first heat transfer faceand isolated from the first inner channel.
 8. The additivelymanufactured heat transfer device of claim 1, wherein the enclosureportion includes a second, opposing heat transfer surface.
 9. Theadditively manufactured heat transfer device of claim 1, wherein the atleast one passage is configured to guide radio transmission through theheat transfer device.
 10. A heat transfer device, comprising: a housinghaving a planar heat transfer face, and an internal wall structureforming a first channel inside the housing configured to conduct heatfrom the heat transfer face to a fluid, the housing and internal wallstructure forming a single additively manufactured unit, wherein theinternal wall structure forms at least one passage through the heattransfer device, perpendicular to the heat transfer face, isolated fromthe first channel and configured for guiding radio transmission throughthe heat transfer device.
 11. The heat transfer device of claim 10,wherein the internal wall structure defines a second channel inside thehousing configured to conduct heat from the heat transfer face to afluid.
 12. The heat transfer device of claim 11, wherein the first andsecond channels are configured to additively remove heat from the heattransfer face.
 13. The heat transfer device of claim 10, furtherincluding a first fluid intake port and a first fluid outtake portconnected to the first channel and configured to direct a flow of acoolant fluid through an outer wall of the housing.
 14. The heattransfer device of claim 10, further including a structural attachmentfeature, wherein the housing, the internal wall structure, and thestructural attachment feature form a single additively manufacturedunit.
 15. The heat transfer device of claim 10, wherein the at least onepassage is configured to guide microwave transmission through the heattransfer device.
 16. A method of manufacturing a heat transfer device,comprising: printing a first housing having an external heat transferface, and an internal wall structure defining a first inner channelconfigured to channel fluid for cooling the heat transfer face, anddefining at least one passage through the heat transfer deviceperpendicular to the heat transfer face and isolated from the firstinner channel, wherein the at least one passage is configured to guideradio transmission through the heat transfer device, and the firsthousing and internal wall structure are formed of a single additivelymanufactured unit.
 17. The method of claim 16, further comprising:printing a first fluid intake port connected to the first inner channel,configured to direct flow of a coolant fluid through an outer wall ofthe first housing into the first inner channel, and printing a firstfluid outtake port connected to the first inner channel, configured todirect flow of a coolant fluid through an outer wall of the firsthousing out of the first inner channel.
 18. The method of claim 16,wherein the printing step includes: forming a second inner channelconfigured for cooling the heat transfer face, the first and secondinner channels being isolated from each other.
 19. The method of claim16, wherein the first housing has a second external face parallel andopposite the external heat transfer face, and the passage extends fromthe external heat transfer face to the second external face.
 20. Themethod of claim 16, further comprising: printing a second housing havingan external heat transfer face, and an internal wall structure defininga first inner channel configured for cooling the heat transfer face,wherein the second housing is configured for assembly with the firsthousing on opposite sides of an electronic circuit device.